This invention relates to novel lactic acid bacteria of the genus Lactobacillus. More particularly, it relates to novel lactic acid bacteria of the genus Lactobacillus capable of lowering cholesterol in blood and liver without exhibiting the properties proper to known lactic acid bacteria of the genus Lactobacillus, that is without exhibiting deconjugation of conjugated bile acids, which are believed to raise the risk of cancer of large intestine and inhibition of absorption of lipid nutrients, such as essential fatty acids or fat-soluble vitamins.
There have so far been made a number of reports on the lactic acid bacteria of the genus Lactobacillus showing the lowering of cholesterol in blood. For example, it was reported by Grunewald in J. of Food Science 47: pages 2078 to 2079 (1982) that the serum cholesterol level could be significantly decreased (p&lt;0.05) when rats were given feeds containing 10% of fermented milk by Lactobacillus acidophilus for four weeks. It was also reported by Gilliland et al. in Applied and Environmental Microbiology 49: pages 377 to 381 (1985) that the rise in the serum cholesterol level in pigs fed with high cholesterol feeds could be significantly inhibited when feeding the pigs with Lactobacillus acidophilus which was derived from the intestinal tract of the pigs and which had the ability of growth in the presence of bile acids in vitro and the ability of metabolizing cholesterol. In addition, it was reported by Suzuki eL al. in Animal Science and Technology 62 (6): pages 565 to 571 (1987), that the effect in suppressing the rise in serum cholesterol level was recognized in rats given the Lactobacillus acidophilus--fermented milk together with high cholesterol feed for 12 days, and that the lactic acid bacteria decreased the absorption of cholesterol micelle from the intestinal tract.
On the other hand, bile acids are synthesized in vivo in the liver from cholesterol and are contained in bile. They are useful in digestion and absorption of lipids and are usually bound by amido-linkage with glycine or tautinc to give a conjugation form so as to exist as taurocholic acid or glycocholic acid. If the conjugated bile acids are deconjugated in the intestines, they become hardly susceptible to absorption in the lower intestine. If the bile acids are converted in the large intestine by enterobacteria into secondary bile acids, they exhibit harmful carcinogenicity. Gilliland et al. reported in Applied and Environmental Microbiology 33: pages 15 to 18 (1977) that Lactobacillus acidophilus isolated from human intestinal tract unexceptionally exhibited deconjugation activity of bile acids.
In keeping up with changes in our daily diet after the European and American type diet and in our living style, the heart disease recently has come to rank highly in Japan among the causes of death. While it is encouraged to decrease the ingestion of animal fats containing a large quantity of cholesterol that causes arteriosclerosis, to increase chances of bodily exercises in our daily life or to refrain from smoking as danger factors, as much as possible, it is usually difficult to change our long nurtured life custom. Although pharmaceuticals effective for hyperglycemia have been developed, they are frequently susceptible to dangerous side effects. Recently, attention is directed to diet therapy which is effective for less serious cases of hyperglycemia. Under such situation, there has been desired an ingredient among highly palatable and readily ingestible foods capable of preventing hyperglycemia as the main cause of the heart disease.
Some of the lactic acid bacteria have been reported to decrease the serum cholesterol, as previously discussed. Although the detailed operating mechanism is not known, such decrease in serum cholesterol is felt to be ascribable to cholesterol adsorption (Bottazzi et al., Annual Microbiology 36: pages 1 to 6, (1986)), to adsorption of bile acids, or to deconjugation activity of bile acids such as taurocholic acid or glycocholic acid by lactic acid (Gilliland et al. (1977)). However, it has also been pointed out that such bile acid deconjugation has a latent risk that free cholic acid is produced to inhibit the cholesterol absorbtion of the conjugated bile acids and to inhibit absorption of nutrients such as fats or fat-soluble vitamins (Rambaud et, al., Microbiology Reviews 12: pages 207 to 220 (1993)). For example, deconjugation of bile acids in the upper part of the small intestine is clinically well known to produce insufficient lipid absorption and diarrhea (King and Toskes Gastroenterology 76: pages 1035 to 1055 (1979)). In raising the livestock, germ free animals gain body weight more significantly than usual animals having enterobacteria (Coats et al., British J. of Nutrition 13: pages 205 to 212, 1959). Suppression of deconjugation activity of bile acids by enterobacteria leads to improved growth of animals (Feighner and Dashkevicz, Applied Environmental Microbiology 53: pages 331 to 336 (1987)) so that the deconjugation activity of bile acids is thought to have a crucial role in digestion and absorption of nutrients. On the other hand, the deconjugated bile acids are hardly re-absorbed in the ileum and hence are liable to be transferred to the large intestine where it is converted to secondary bile acids which are promotors of cancer. Thus, the deconjugated bile acids are thought to increase the risk of cancer in large intestine (Hill, Mutation Research 238: pages 313 to 320 (1990)).
However, there lacks up to now a report on means for creating lactic acid bacteria of the genus Lactobacillus which exhibit the lowering of cholesterol in blood without exhibiting the deconjugation of bile acids and the inhibition of absorption of nutrients, or a report on such lactic acid bacteria of the genus Lactobacillus per se.